As one of the fluorescence spectrometers, a capillary electrophoretic apparatus is exemplified. The capillary electrophoretic apparatus is mainly used for determining a base sequence or a base length of DNA. In capillary electrophoresis, a thin tube which is referred to as a capillary is filled with a migration medium such as a gel and a DNA fragment of a sample is migrated within this capillary. In addition, the time required for the sample to finish migration of only a constant distance (normally, from one end of the capillary to the other end) is measured so as to investigate the length of the DNA fragment. Each sample, in other words, each DNA fragment, is labeled by a fluorescent pigment, and a fluorescent signal of the migrated sample is detected by means of an optical detector placed at the terminal of the capillary.
A multi-focus system disclosed in PTL 1 is exemplified as one of systems of irradiating a plurality of capillaries with a laser beam. In this system, a capillary positioned on one end or both ends of a capillary array configured to include the plurality of capillaries arranged on a planar substrate is irradiated with a laser beam. In addition, the radiated laser beam propagates capillaries adjacent to each other one by one to traverse the capillary array. Light emission caused in the capillary array is detected by a photodetector. A sample including DNA labeled by a fluorescent pigment is introduced into the capillary, and the sample is irradiated with a laser beam such that the laser beam propagates the plurality of capillaries arranged in a row. The DNA which is fluorescence-labeled by the laser beam radiated to the capillary emits fluorescent light. By measuring the fluorescent light from each capillary, it is possible to analyze DNA of the sample introduced into each capillary. The same applies to a case of analyzing protein, or the like.
In the fluorescent light detection of the apparatus described above, the fluorescent light in each fluorescent pigment obtained by irradiating the terminal of the capillary with a laser beam having a specific wavelength is separated by means of a diffraction grating, and an image in a space direction and a wavelength direction is detected by a two-dimensional detector such as a CCD. An image captured by the detector is stored as spectral data of a specific capillary, and used for data analysis. A fluorescence spectrometer disclosed in PTL 2 continuously scatters the obtained fluorescent light using a diffraction grating, and performs analysis by measuring a spectrum (in actuality, discrete for every pixel).
Currently, the use of an analyzer using a fluorescence detector has been extended from a research market to an application market, and it is necessary to cope with a sample having different concentration (detection intensity is varied). The above-mentioned capillary electrophoretic apparatus is one of the above. A major fluorescence detector which has been used in the related art detects the fluorescent light by a single detector. A dynamic range or a detection range of the detector depends on excitation efficiency of a fluorescent sample, a NA of a camera lens, or performance of a two-dimensional detector.
In a device in which a wide dynamic range or a detection range is necessary, a method is used, in which a beam splitter or a filter is provided in the middle of an optical path to split a detection image and a plurality of images having different fluorescent intensity is obtained by a plurality of detectors. However, since a plurality of expensive detectors is necessary, there is a demerit such as an increase in cost of the apparatus and an increase in size of a detection unit.
In addition, the fluorescent intensity depends on the irradiation detection time or the irradiation intensity. Therefore, it is possible to obtain data having different intensity by controlling a parameter of an irradiation side. Thus, a method is suggested, in which the period of the irradiation time or the detection time is elongated or reduced during analysis of using a single detector so as to obtain data having different fluorescent intensity. However, in an apparatus in which data is obtained in times series, measured points per a unit time may be reduced and sampling points necessary for obtaining data may be insufficient.